Cohesion of Water

Developer:

Grade Levels:

Discipline:

Physical Science

Objectives:

  1. Students will be able to observe cohesion of water.
  2. Students will determine the number of drops of water a penny can hold.
  3. Students will compute an average (mode) of several trials.

Vocabulary:

COHESION = molecular attraction by which the particles of a body are united throughout the mass.

MASS = the amount of matter in an object.

MOLECULE = the smallest particle of a substance that retains the properties of the substance and is composed of one or more atoms.

ATOM = the smallest particle of an element that can exist either alone or in combination

ELEMENT = a simple substance that cannot be broken down into simpler substances.

Background:

Hypothesis:

It will be found that a penny will hold ______ drops of water.

Materials:

Penny

penny

Eye Dropper

eyedropper

water

Procedure:

  1. Use the eyedropper to drop water onto the penny one at a time until the water flows off the penny.

  2. Count the drops. (The last drop that stays on the penny is the numer of drops that the penny can hold.)

  3. Record the number of drops.

  4. Repeat twice so that you have 3 measurements.

  5. Compute the mode (sum of the three trials divided by 3).

Explanation:

Questions:

  1. How did the results compare with the prediction?

  2. Were you surprised at the number of drops you were able to put on the penny?

  3. How do you think water was able to bead up on the penny like that?

  4. Define Cohesion:

  5. Define this property in your own words

Inference:

It was found that a penny will hold an average of _____ drops of water.


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